This invention relates generally to methods and apparatus for gundrilling (deep hold drilling) or cold forming workpieces on gundrilling machines, heading machines, or thread rolling machines, including combination machines like bolt making machines.
In thread rolling dies to which the invention relates, workpieces are transformed into finished screws by a rolling process as the workpieces pass between a pair of elongated generally planar dies. One of the dies is stationary, and the other die is displaced relative to the other to produce a surface material flow on the workpiece to thereby form a continuous helical thread path on the screw. In the thread rolling die machines for which the invention has particular applicability, a shorter die of a pair of dies is held in stationary relationship while the longer die is moved in a direction generally parallel to a longitudinal reference plane. The axis of rotation of the body of the workpiece travels longitudinally as the workpiece rolls between the pair of dies. The diameter of the finished thread is controlled by the diameter of the workpiece and the distance between the dies at the finished end of the stroke. The dies are configured so that as the workpiece rolls across the dies, the desired threading is formed on the workpiece. Thread rolling is also accomplished using cylindrical or planetary dies and machines and this invention is applicable to all known configurations.
To be competitive in the marketplace, manufacturers must maintain a cost effective manufacturing environment and must be responsive to customer requests. These two goals can often be in conflict. For example, costs may be reduced by maintaining low inventories of raw materials, finished products, and tooling. However, if such inventories are too low, the manufacturer may be unable to promptly respond to a customer order. Manufacturers typically strike a balance where they maintain some minimum inventory of raw materials and/or finished product such that a hypothetical order may be filled within an acceptable time period. Such manufacturers also monitor their tooling to ensure that new tooling is received just as the old tooling reaches the end of its effective lifetime.
Each set of tools has an effective lifetime which is defined by a maximum number of operating cycles which may be performed before the accumulated wear precludes further use. There are several factors which may change the effective lifetime of a tool set. For example, the rate of tool wear is proportional to the material hardness of the workpieces, where the rate of die wear increases as the material hardness increases. Consequently, the effective lifetime of a die set which is used to form threads on workpieces composed of relatively hard stainless steel is lower than the effective lifetime of an identical die set which is used to form threads on workpieces composed of relatively soft carbon steel.
Effectively monitoring the effective lifetime of tool sets which are utilized to produce many short production runs and/or which are utilized to produce components composed of different materials can be problematic. Although the number of components produced in each run or of each material may be fairly easily determined, conventional record keeping systems for tracking the effective lifetime of the tool set are cumbersome, resulting in errors which can be quite costly to the manufacturer and supplier.